My Mercedes engine light came on and I used my OB and it is throwing a Po300, PO171 and a PO174. What do those codes mean?


Asked by Aug 05, 2013 at 08:27 AM about the 2003 Mercedes-Benz S-Class S500

Question type: Maintenance & Repair

Just trying to find out what the codes mean and what I can do to fix.  Basically the car runs really good.  It kinda of misses or is rough when cold but that changes when warms up.

5 Answers

Tom Demyan

P0300 is a misfire, P0171 amd P0174 are a vacuum leak. Check all your hoses for leaks. Fire up the car and open the hood, see if you can hear any leaks, move the hoses around.

3 out of 3 people think this is helpful.

Thank you very much for your help. I am always dumbfounded sometimes at the different replies people give you. I had a mobile mechanic tell me that all I need was a coil. Your answer sounds more correct. Thanks again, Mr. Cloyd

Tom Demyan

Scan for codes again after you find the vacuum leak, see if the P0300 comes back, which can be a coil.

Michael Griffin

Ignetion coil cause miss fire !


Maybe the time to change AIR FLOW MITER Sensor, Make sure its not for eBay or cheap from China. Try to get original one.

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